It is well known in the art to use steerable (or tracking) antennas to communicate with a relatively moving target over a scan angle. Especially in the aerospace industry when the antenna is on board of a spacecraft, such steerable RF (Radio Frequency signal) antennas preferably need to have precise pointing, high gain, low mass, and high reliability.
Satellites often contain two (2) degree of freedom pointing devices to communicate, sense, etc. with other satellites or bodies. Since the distances are large, the pointing accuracy and resolution is critical.
The payload of these pointing devices is variable. Some payloads are full antennas, portions of an antenna, sensors, etc.
Many different pointing devices have been devised in the past. The simplest one being two rotary actuators (RA) assembled in a sequential chain and holding the payload, such as a reflector, as shown in FIGS. 1a and 1b. Especially when relatively small scan angles are required, such as below +/−30 degrees for example, these types of pointing devices have many disadvantages, or at least a few, among the following list:                high profile;        heavy mass, structurally inefficient;        high cost;        low accuracy;        low resolution;        low reliability;        need for Hold down and Release Mechanisms (HRM);        requires fixed predetermined stowed position for launch;        need for moving harness (RF rotary joint, electrical wiring, etc.); and/or        reduced RF performance in the case of a reflector pointing mechanism,        
Accordingly, there is a need for an improved antenna pointing system.